Question

If the radius of a circle is increased by 10% then percentage of increase in its area is?

Answer 1

da/dr = 2 pie r

da/a = 2 pie r .dr/a
AS GIVEN dr/r = 10/100=1/10

= 2 pie r dr/ pie r .r
= 2 dr/r
= 2/10
= 1/5

SO 20%